The use of internally mounted end prep tools is generally known in the art. End prep tools are typically used, for example, to prepare a pipe for welding by cutting, machining and/or beveling the end of the pipe. The conventional end prep tool mounts or clamps to the inside surface of the pipe with a mandrel having three expandable clamps spaced about 120° apart. The clamps generally expand simultaneously when pulled up a 15° taper by a draw rod. When used with a pipe or tube that is perfectly round, this type of conventional end prep tool is self-centering and mounts securely to the inside surface of the pipe.
In pipes or tubes of larger diameters (e.g., greater than 16 in.), however, the pipe roundness and wall thickness are usually inconsistent. A standard 24 in. schedule 120 pipe, for example, often has an egg shape and a wall thickness varying by as much as 50% from the expected thickness of 1.812 in. Because of the out of roundness in such large pipes, the conventional self-centering end prep tools typically clamp off-center. As a result, the surface that is prepared or machined is also off-center.
Another drawback of conventional end prep tools relates to the tool feed mechanism. The conventional end prep tool includes a star wheel that rotates a feed screw to advance a tool carriage. The star wheel rotates by engaging a structure on the tool housing as the tool rotates. The conventional star wheel often misaligns, causing the feed mechanism to jam and a failure of the tool to advance.
A further drawback of the conventional end prep tool is the difficulty of cutting certain types of bevels. With smaller pipes having thinner walls, a single bevel is used (e.g., a 37½° bevel on a ¾ in. wall thickness). On larger pipes having thicker walls, however, a compound bevel is often required (e.g., a 37½° to a 10° bevel). The conventional end prep tools have difficulty cutting a compound bevel because of the degree change in the middle of the prep.
Accordingly, there is a need for a tool centering and mounting system for mounting a tool substantially aligned with the theoretical center of a pipe having an inconsistent thickness and roundness. There is also a need for an internally mounted end prep tool for preparing the end of a pipe (e.g., by boring and/or cutting) with respect to the theoretical center of the pipe. There is a further need for an end prep tool capable of cutting a compound bevel more easily.